Safety for occupants of a vehicle involved in an accident has been improved. Recently, in addition to occupant safety, pedestrian safety has been required to protect pedestrians from fatal injuries in the accident. Therefore, it becomes important to detect a collision of the vehicle with the pedestrians.
A collision detection system has been proposed that detects a collision of a vehicle with an object by a pressure sensor installed between a bumper absorber and a bumper reinforcement of the vehicle. A load plate made of resin or metal is interposed between the bumper absorber and the pressure sensor.
In such a collision detection system, a mat-type pressure-sensitive sensor is sometimes used as the pressure sensor. When used as the pressure sensor of the collision detection system, the mat-type pressure-sensitive sensor needs to have a large pressure-sensitive range to sense high pressure.
However, whereas a mat-type pressure-sensitive sensor having a small pressure-sensitive range is cheap, a mat-type pressure-sensitive sensor having a large pressure-sensitive range is costly. Further, a mat-type pressure-sensitive sensor is partially made of resin, and the resin portion is deformed when receiving high pressure. The resin portion may remain deformed even after the high pressure is removed. As a result, the mat-type pressure-sensitive sensor may—not return to its original shape and may produce inaccurate output.